To the Editor: In their discussion of disclosure
of HEDIS quality scores, Dr McCormick and colleagues1 appear
to assume that HMOs can influence the quality of medical care. I believe that
there is insufficient evidence for this assumption.

The HEDIS measures were initially designed to compare the cost and quality
of health care delivered to capitated populations by a homogeneous group of
tightly managed staff and group model HMOs. It is questionable whether current
health plans—which typically involve large, overlapping heterogeneous
networks of physicians, hospitals, and clinics—can influence the quality
of care delivered to populations they serve. McCormick et al imply that HMOs
deliver medical care, when in fact they act more as insurance companies. It
is physicians, not health plans, who provide care for patients.